Hands on with the super tiny arudino: FemtoDuino

We originally heard about the FemtoDuino last year. It looked good enough and tiny enough, but we didn’t really have a need for it. Recently though, we started on a new project (which you can follow on the forums!) which required an easy modification to an existing circuit. Space and weight were quite important so we decided to pick up a couple femtoduinos at $25 each, and give them a try.

These things are tiny. Their foot print is 20.7×15.2mm. You can see in the picture below, with a quarter for reference. Tiny. Frankly, there’s not much to say about them. They’re an Atmega328 that is arduino compatible. I plan on using my redbull Arduino to program this thing, since you need to bring your own serial interface.

If you’re anything like me, you have atrociously sloppy soldering and shaky shaky hands. I was a bit concerned about actually getting those wires soldered in without bridging the pads. I was able to pull it off though. Here’s a video so you can see how horrible my soldering technique and equipment are.

I really don’t have any complaints about this thing, it works just like an arduino but smaller. The closest thing to a complaint is that the silk screening is a bit blurry making it difficult to read which pins are what. It isn’t horrible, but it isn’t perfect either. We really couldn’t think of much else so we decided a haiku would cover it.

With that soldering iron it’s not your fault your soldering is terrible. Seriously. I got a $30 hakko 15w iron that isn’t temp controller or anything, and it’s was much better than the ratshack garbage. I used that to do 0603 stuff. But even that isn’t all that great in the long run. I would highly recommend an aoyue 937+. It’s only $58, and it’s a digital temp controller iron. I’ve been using mine for a couple years now, I absolutely love it.

When I was doing a lot of board population soldering for someone I found that blu-tack is an excellent tool for holding the boards in place as they will stay put but you can quickly & easily move them about the desk without having to undo vice jaws. Just don’t get blu-tack too hot or it goes extremely stringy & sticky which can make it difficult to remove from inbetween IC legs.

What really bothered me was the way the tip moved in the “socket.” Agghhh.

Years ago, after going through many cheap irons, I finally bought a temperature controlled soldering station. What an amazing piece of equipment. It’s difficult to explain just how wonderful it is to have proper tools.

I’ll be interested to see how the Femtoduino works out, as I’ve been considering it for a project. You might want to obtain a more delicate and temperature-controlled soldering iron for future work. That thing looks more suited to copper plumbing.

I think the Teensy is a much better choice. It is not even twice the size (.81″ x .6″ vs. 1.2″ x .7″). It also has many advantages over the FemtoDuino:
1. A built-in USB port, so no FTDI cable or Arduino needed for programming.
2. Normal 0.1″ connectors, so standard header pins can be used, and soldering is much easier.
3. Ability to act as an HID USB device (keyboard, mouse).
4. Much more reasonably priced: $16 (w/o pins) + $3.80 shipping for up to 2 pieces.

Hi Eric,
1. The built-in USB port is now found in the FemtoduinoUSB ( https://tindie.com/shops/femtoduino/femtoduino-with-usb/ )
2. If we had used 0.1″ connectors, we wouldn’t have the smallest board with all the pins. That’s what the Femtoduino Breakout board is for
3. Good point… but at the size it’s at, there’s not much room for anything else.
4. We’re not mass fabricated yet. The more people that support us through the tindie fundraisers, the sooner the Femtoduino can be mass-fabricated, and made inexpensive. See https://tindie.com/shops/femtoduino/femtoduino-1/

Finer-pitch solder can help for those small holes, but what helps the most is some sort of board clamp that allows you to rest your hand. It doesn’t need to be professional. Binocular microscope a’int bad either. :)

Can I recommend getting a soldering iron made after 1950? One with a long skinny tip? One of the orange Weller student irons with a replacement tip? (The default tip on the Weller is big enough to dig trenches with…)

May I suggest using soldering flux? I hand solder most of the board (including the ATMega328p-mu), but that’s only possible due to generous amounts of flux. It keeps the solder from sticking everywhere.

Or use good solder wire. I prefer Multicore Crystal 511. It’s got excellent wetting capabilities, and flows very nicely, even on somewhat dirty or corroded surfaces. Because of the halide additive, I recommend cleaning up the residue. For 99% of SMT work, I don’t use extra flux.

Amen! Lots of “hackers” buy the cheapest junk solder they can find. Last spool of that stuff Cost me $40.00.. I hear a lot of guys at the Hackerspace whine that I’m out of my mind spending that kind of money on solder…

This is the best iron for the price and that tip makes it just as good as anything else. Anybody who tells you anything different is just throwing out names like they mean anything other than you get a fancy box with a fancy set of instructions in it.

I have shaky hands as well. What really helps is to rest your elbow on a pillow that is soft enough to tilt up and down easily while still providing a little support. Doesn’t eliminate the shakes entirely, but dampens it enough to do some pinpoint work.